Technical Field
The present disclosure relates to the field of ranging based on a time of flight calculation, and in particular to a ranging device with imaging capabilities.
Description of the Related Art
SPAD (single-photon avalanche diode) arrays can be used for a variety of applications, including for ranging, for 2D or 3D gesture recognition and for 3D imaging. A device for such applications generally comprises a light source for transmitting an optical pulse into the image scene. The light reflected back from any object in the image scene is detected by the SPAD array, and used to determine the time of flight of the optical pulse. The distance from the object to the device can then be deduced based on this time of flight.
The detection by the SPAD array of the returning optical pulse is based on event detection in the cells of the SPAD array. In particular, each cell will provide an output pulse when a photon is detected, and by monitoring the events, the arrival time of the return pulse can be estimated.
A SPAD array comprising columns and rows of SPADs permits scene content to be captured in two dimensions by the array. The outputs of the SPADs are combined and provided to a phase detector in order to estimate the time of flight.
A difficulty is that, depending on the 2-dimensional scene content, some of the SPADs in the array may provide an output signal having a poor signal-to-noise ratio (SNR), leading to inaccuracies in the time of flight calculation.
There is a need in the art for a method and device for compensating for such pixels in a simple and efficient manner.